Austenitic stainless steel

ABSTRACT

Austenitic stainless steel essentially consisting of 1.0-2.5 wt. percent Si, 1.5-5.0 wt. percent Mn, 1.0-4.0 wt. percent Cu, 6.09.0 wt. percent Ni, 15.0-19.0 wt. percent Cr, not more than 0.06 wt. percent C, nor more than 0.03 wt. percent N, and balance Fe and incidental impurities, in which the total content of C and N in the solid solution state is less than 0.04 wt. percent has excellent drawability and stretchability and is highly resistant to delayed cracking. Although the austenite phase of this steel is unstable to strain-induced martensitic transformation, the steel is highly resistant to delayed cracking. The said low content of C and N in the solid solution state is achieved by known decarbonization processes or by addition of a limited amount of Al and/or Ti to the melt.

United States Patent Fujioka et al. 1 Oct. 7, 1975 15 1 AUSTENITICSTAINLESS STEEL 3.337.331 8/1967 Ljungberg 75/128 A x 1751 e Fuiioka;K2190 312231333 31133? Z11ZZ1".;111TJ.1-.......ji;.'.'i52/1535)? lTakashl lgawa, of 3,697,258 10/1972 Floreen 75/128 C i" Japan 3,795,5073/1974 Allen 75/124 [73] Assignee: Nisshin Steel Co., Ltd., Tokyo.

Japa Primary Examiner-L. Dewayne Rutledge Assistant Examiner-Arthur 1.Steiner 1221 Flled: 1974 Attorney, Agent. or Firm-Ladas. Parry, VonGehr, [21] A L N 461,335 Goldsmith & Dcschamps 130 Foreign ApplicationPriority Data 1 1 ABSTRACT Apr. 21, 1973 Japan 48-44656 Austeniticstainless steel essentially consisting of 1.0-2.5 wt. percent Si,1.5-5.0 wt. percent Mn. [52] 1.1.8. Cl. 75/125; 75/124; 75/128 A;1.0-4.0 wt. percent Cu, 6.0-9.0 wt. percent Ni.

75/128 C; 75/128 N; 75/128 T 15.0-19.0 wt. percent Cr, not more than0.06 wt. per- 1 1 C C 38/02,C22C 38/06. cent Co not more than 0.03 wt.percent N. and bal- C22C 38/42 C22C 38/58 ance Fe and incidentalimpurities, in which the total [58] Field of Search 75/124, 125, 128 A,128 C, content of C and N in the solid solution state is less 75/128 N,128 T than 0.04 wt. percent has excellent drawability and stretchabilityand is highly resistant to delayed crack- [56] References Cited ing.Although the austenite phase of this steel is unsta- UNITED STATESPATENTS ble to strain-induced martensitic transformation, the 2 I50 9013H939 Amess steel is highly resistant to delayed cracking. The said 3 510/1964 Lulawjm low content of C and N in the solid solution state is3154412 0 19 Kasak achieved by known decarbonization processes or by3,159,480 12/1964 Copson... addition of a limited amount of Al and/0r T1to the 3,282,686 11/1966 Allen melt. 3,303,023 2/1967 Dulis et a1 75/1286 Claims, 1 Drawing Figure AUSTENITIC STAINLESS STEEL BACKGROUND OF THEINVENTION with high elongation because of their high work hardeningcoefficient in addition to their excellent corrosion resistanceproperties, and therefore they are formed into desired shapes by deepdrawing and are widely used in various technical fields.

As the steel species suitable for such cases, A151 301 0.15 percent C,l.00 percent Si, 2.00 percent Mn, 0.030 percent S, 0.045 percent P,16-18 per cent Cr, 6-8 percent Ni), AISI 304 0.08 percent C, l .00percent Si, 2.00 percent Mn, 0.030 percent S, 0.045 percent P, 18-20percent Cr, 8-12 percent Ni), A151 305 0.12 percent C, l.00 percent Si,2.00 percent Mn, 0.030 percent P, 0.045 percent S, 17-19 percent Cr, -13percent Ni), etc. are known. (In this specification, all the percentagesconcerning steel composition are those by weight.)

From the view point of plastic deformation, AISI 301 is preferably usedas the material for stretching, because when this steel is subjected toplastic deformation, strain-induced martensite is easily formed, whichprevents local neckings and gives remarkable elongation to the material.However, if this steel undergoes drawing in which compression strain isgiven to the material and the material retains tension stress afterdrawing, delayed cracking occurs within a short period of time when thesteel is simply allowed to stand in the at mosphere after drawing.

A151 304 is somewhat less sensitive to delayed cracking and theincubation time before occurrence of delayed cracking is longer. Butwhen this steel is subjected to severe deep drawing, still delayedcracking often happens. Therefore, even A181 304 has to be annealed manytimes in the course of drawing forming in order to avoid the delayedcracking when it is shaped by severe drawing. Such annealing treatmentnot only adds to the manufacturing cost, but coarsens the crystal grainsand thus deteriorates the surface of finished products or causesprecipitation of chromium carbide which may locally impair corrosionresistance of finished products if the annealing conditions are notstrictly controlled.

AISI 305 is more stable against strain-induced martenistictransformation and less sensitive to delayed cracking. However, A131 305is inferior in stretchability and deep drawability because of its lowerWork hardening coefficient. The lower work hardening coefficient is dueto high Ni content of the steel, which means that the material isexpensive, too.

Concerning the mechanism of occurrence of delayed cracking after drawingforming in these materials, F. W. Schaller et al. presented a theory(Sheet Metal Industries, Oct. 621 1972)). According to them, delayedcracking is caused by the strain-induced martensite which is moresensitive to occluded hydrogen, therefore the material in which itsaustenite phase is less stable against the strain-induced martensitictransformation is more liable to the delayed cracking. This theory wellcorresponds to sensitivities to delayed cracking of a series ofmaterials including A151 301, 304. 305, etc.

More recently, austenitic stainless steels of this kind in which aportion of Ni is replaced by Cu are known. (US. Pat. No. 3,282,684 0.l5percent C, 0.40-2.00 percent Mn, 0.15- 1.00 percent Si, 16-19 percentCr, 5.5-8.0 percent Ni, 0.5-3.5 percent Cu, 0.04-0.10 percent N andbalance Fe) and U.S. Pat. No. 3,282,686 0.l5 percent C, 0.5-2.00 percentMn, 0.15-1.00 percent Si, 16-19 percent Cr, 6.6-7.9 percent Ni, 1.5-2.9percent Cu, 0.03 percent N and balance Fe)) Cu is effective forinhibiting the strain-induced martensitic transformation as well as Ni.

We extensively and experimentally studied the mechanism of occurrence ofdelayed cracking and found that the delayed cracking does not occur whenthe total content of C and N that are present in the state of solidsolution in the steel is less than 0.04 percent, even if the austenitephase thereof is very unstable against straininduced martensitictransformation and a large amount of strain-induced martensite is formedin the course of drawing forming, delayed cracking does not occur.

In the above-mentioned A181 301, 304 and 305, the C content is definedas less than 0. 15 percent, 0.08 percent and 0.12 percent respectively.But they usually contain 0.04 percent or more C and 0.015 percent ormore N and the total of the two elements is 0.055 percent or more. Inthe steel of U.S. Pat. No. 3,282,684, 0.04-0.10 percent N isintentionally added.

That is, any attempt to improve resistance to delayed cracking of thesesteels by restricting the total content of C and N in the solid solutionstate to less than 0.04 percent had not been made prior to thisinvention of ours. It was thought that if the content ofC and N in thesolid solution state were lowered, the Ni content should be increased tocompensate for the decrease in the contents of C and N as theaustenite-forming elements, which would result in rise in manufacturingcost and decrease in work hardening coefficient, since the fact thatdelayed cracking can be prevented by restricting the contents of C and Nin the solid solution state was not known.

In this invention of ours, the decrease in work hardening coefficientcaused by decrease in the contents of C and N in the solid solutionstate is compensated for by increase in the contents of Si, Mn and Cu,and thus an austenitic stainless steel which has excellent formabilityand is highly resistant to delayed cracking after deep drawing isprovided at the price of the same level as that of A18] 304.

SUMMARY OF THE INVENTION According to this invention, stainless steelwith excellent drawability and stretchability and high resistance todelayed cracking essentially consisting of 10-25 percent Si, l.55.0percent Mn, 15-19 percent Cr, 10-40 percent Cu, 6.0-9.0 percent Ni, notmore than 0.06 percent C, not more than 0.03 percent N and balance Fewith incidental impurities, in which the total content of C and N in thesolid solution state is less than 0.04 percent is provided.

The austenitic stainless steel of this invention contains Si in anamount of 1.0-2.5 percent, preferably 10-20 percent and more preferably1.2-1.8 percent; Mn in an amount of 1.5-5 .0 percent, preferably 15-30percent, and more preferably 1.8-2.8 percent; Cu in an amount of 10-40percent, preferably 1 .0-30 percent and more preferably l.5-2.5 percent;Ni in an amount of 6.0-9.0 percent, preferably 6.5-8.5 percent and morepreferably 6.7-8 percent; and Cr in an amount of -19 percent, preferably15.5-17.5 percent and more preferably 16-17 percent; and may contain Aland/or Ti in an amount of up to 0.5 percent, preferably up to 0.4percent and more preferably up to 0.3 percent in order to fix C and N sothat the total amount ofC and N in the solid solution state is less than0.04 percent. In any case, the total amount ofC and N in the solidsolution state must be less than 0.04 percent, and preferably less than0.03 percent.

Si improves work hardening property of austenite phase itself, and theeffect is proportional to the content. The austenitic stainless steel,in which the content of C and N in the solid solution state isrestricted. is inferior in work hardening coefficient. Therefore, inthis invention Si is an indispensable element that conpensates for thedrop of the work hardening coefficient. Also Si improves resistance topitting corrosion. At least 1.0 percent Si is required to accomplishthis object. But Si in excess of 2.5 percent will cause formation ofS-ferrite, which impairs hot workability or causes hot cracking. The Sicontent is preferably 1.0-2.0 percent, and more preferably 1.2-1.8percent.

Mn has the effect of inhibiting strain-induced martensitictransformation of the austenite phase as well as Ni, but is differentfrom Ni in that it strengthens the strain-induced rnartensite andenhances work hardening coefficient and improves stretchability anddrawability of the material. However, the S-ferrite-inhibiting effect ofMn is not so strong as Ni. And a rather high percentage thereof is lostduring steel making. So this element does not contribute so much to costcutting as expected from the difference in prices of these elements. Thereasonable content of Mn is within a range of 1.0-5.0 percent,preferably 1.5-3.0 percent and more preferably 1.8-2.8 percent.

Cu, as well as Ni, has the effect of inhibiting straininducedmartensitic transformation of austenite phase and strengthens thestrain-induced rnartensite, and improves work hardening coefficient ofthe material as the result. However, too much Cu impairs hotworkability. The reasonable content of Cu is 1.0-4.0 percent, preferably1.0-3.0 percent and more preferably 1.5-2.5 percent.

Ni, which is an expensive element, does not contribute so much to workhardening property of the austenite phase or strain-induced rnartensiteper se and therefore it is desirable to use this element at a content aslow as possible. The reasonable content, thereof, is 6.0-9.0 percent,preferably 6.5-8.5 percent and more preferably 6.7-8 percent.

Cr contributes to corrosion resistance in proportion to the contentthereof. But at too high content, it causes formation of S-ferrite andimpairs hot workability. Thus the Cr content is limited to 15-19percent, the preferable content range being 15.5-17.5 percent and morepreferably range is 16-17 percent.

The total content of C and N in the solid solution state must be lessthan 0.04 percent. This can be achieved by reducing the amounts of C andN by the so-called Vacuum Oxygen Decarbonization Process or Argon OxygenDecarbonization Process. In the ordinary electric steel making processthe total amount of C and N cannot be reduced to less than 0.04 percent,so up to 0.5 percent of Al and/or Ti is added to the melt so as toreduce C and N in the solid solution state to less than 0.04 percent.

A1 fixes N as MN and is effective to reduce N in the solid solutionstate when the N content is high. But high 4 content thereof contributesto formation of S-ferrite. Ti fixes C and N as Ti(C, N) and is effectiveto reduce C and N in the solid solution state. Therefore the content ofAl and/or Ti is limited to less than 0.5 percent and preferably 0.3percent.

The total amount of C (both of the fixed and that in the solid solutionstate) should be 0.06 percent or less. And the total amount of N (bothof the fixed and that in the solid solution state) should be 0.03percent or less. In order to reduce the total amount of C and N in thesolid solution state to less than 0.04 percent, the amounts of the totalC and the total N should preferably be not more than 0.06 percent and0.03 percent respectively. As to the other impurities, the S contentshould be 0.03 percent or less, and the P content should be 0.04 percentor less.

The austenitic stainless steel of this invention can be made by theVacuum Oxygen Decarbonization Process or Argon Oxygen DecarbonizationProcess or by the ordinary electric steel making with the aid of Aland/or Ti as mentioned above. And there is no necessity of explainingthe manufacturing process for the steel in detail here.

The austenitic stainless steel of this invention is characterized inthat it is provided with excellent drawability and stretchability and ishighly resistant to delayed cracking.

BRIEF DESCRIPTION OF THE DRAWING The attached drawing shows drawing testspecimen of the steels of this invention and of the prior art.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS The invention isillustrated by way of examples and comparative examples.

Nine (9) sample heats within the scope of this invention, one sampleheat each of the steels of AISI 301, AISI 304, A151 305, U.S. Pat. No.3,282,684 and U.S. Pat. No. 3,282,686 were prepared by melting in a highfrequency electric furnace of 30 kg capacity. The ingot of each heat wasmade into 0.6 mm X mm X 100 mm plates by successively subjecting to hotforging, solution treatment 1,100C, 1 hr, W.Q. machining, cold rolling,annealing I050C, 10 min, A.C.) and cold rolling. The plates were finallyannealed at l ,O50C for 5 minutes and air-cooled. All the specimen wereprepared under the same conditions.

The chemical analysis of these samples are summarized in Table I. Inthis table the steel of U.S. Pat. No. 3,282,684 is designated asCr-Ni-Cu-N and the steel of U.S. Pat. No. 3,282,686 is designated asCr-Ni-Cu steel.

In the Cr-Ni-Cu-N steel and the Cr-Ni-Cu steel, the Si present is theresidual of the Si that was used for deoxidation and does not functionat all to improve the steel properties. In contrast, in the steels ofthis invention, Si is intentionally added for the enhancement of workhardening coefficient and it is contained in an amount of 1.0 percent ormore.

In the Cr-Ni-Cu-N steel, N is intentionally added in an amount of0.04-0.10 percent in order to stabilize its austenite phase against thestrain-induced martensitic transformation. In the Cr-Ni-Cu steel, the Ncontent is defined as not more than 0.03 percent and the C content isdefmed as not more than 0.15 percent. But in the specification proper,it is explained that the C content should be at least 0.04 percent andthe preferred range is 0.05-0.08 percent. And none of the examples isthe total content of C and N less than 0.08 percent.

Among the steels of this invention, the total content ofC and N of48A02, 48AO3 and 48A09 is in excess of 6 delayed cracking, there issignificant difference between them. That is to say, the austenite phaseof AlSl 305 is markedly stable against the strain-induced martensitictransformation as duly anticipated from the ex- 0.04 percent. But thesenumerical values include the 5 perimental results of Schaller et al. Onthe other hand, amounts of the fixed C and N. That is. these samples theaustenite phase of the steels of this invention is very were dissolvedin an iodine-alcohol solution and the sounstable and martensitictransformation takes place lution was filtered with a filter paperhaving the pore more easily than in AlSl 30l when suffering plasticdediameter of 0.2 micron. The collected residue. which is formation.But, none the less, its delayed cracking sus- Ti(C, N) and/or AlN, wasanalyzed. and in 48AO2 and ceptibility is remarkably low.

Table 2 Properties Hard- 0.2 7( Tensile Elon- Martensite ErichsenConical Limiting ness Yield strength gation percentage (mm) cup drawingHv( 10) (kg/mm) (kg/mm 1%) value ratio Sample 1mm) Steels of 411M01 12523 60 61 35 12.6 27.2 23.10 this 48M07 121 23 60 60 13 12.5 27.4invention 48M) 130 24 61 58 30 13.0 27.0 411M114 118 60 55 33 12.5 27.448M05 122 20 58 59 24 12.9 27.3 48M06 113 19 56 59 [8 12.4 27.0 48A02I08 17 55 60 42 13.1 261.8 48A03 115 20 59 58 12.11 27.2 48A09 113 19 6061 211 13.4 26.9 Comparative AIS] 301 169 2s 30 61 32 14.5 27.0 2.03samples A151 304 165 28 68 53 s 12.0 27.6 2.61 AISI 305 140 26 62 57 011.6 27.3 23.10 Cr-NiCu-N 165 31 67 5s 18 13.0 20.8 2.41 Cr-Ni-Cu l533t) 68 56 2| l2.8 27.2 2.32

48A03 respectively 0.022 percent and 0.021 percent N Although AlSl 305is parallel with the steels of this were found as AlN and there was nocarbon. Therefore invention in delayed cracking susceptibility, theformer N in the solid solution state was 0.0[0 percent and i is inferiorto the latter in stretchability and drawability. 0.009 percentrespectively, and all the carbon existed AlSl 301, Cr-Ni-Cu-N steels andCr-Ni-Cu steels are in the solid solution state in both 48A02. and48A03. ln equal to the steels of this invention in stretchability and48A09 the content of N in the solid solution state was drawability, butare highly susceptible to delayed trace and the content of C in thesolid solution state is cracking. was 0.017 percent.

Table 1 Sample Element C Si Mn P 5 Cr Ni N Cu Ti Al 516615 or 41-1M010.007 1.60 3.00 0.012 0.009 16.73 6.99 0.030 1.99 "13136 0.016 this48M07 0.012 1.71 1.53 0.008 0.01 1 l8.l2 8.90 0.025 1.921 ULICE 0.010invention 48Ml0 0.014 1.20 2.59 0.01 1 0.01 1 17.25 7.53 0.027 2.14trace 0.007 48MU4 0.010 1.53 3.15 0.011 0.010 16.23 15.07 0.0211 1.260.27 0.021 48M05 0.010 1.62 3.17 0.008 0.008 16.19 11.07 0.026 2.97 0.240.010 48M06 0.010 2.40 1.55 0.009 0.008 16.01 8.6] 0.0211 2.00 0.290.010 48A02 0.016 1.53 1.89 0.010 0.010 16.74 11.23 0.032 1.31 mm 0.4348A03 0.020 1.14 2.32 0.009 0.010 16.47 7.73 0.030 2.11 U'IJCB 0.374sA09 0.029 1.62 2.1 1 0.01 1 0.008 16.96 11.25 0.0211 1.78 0.25 0.30Comparative AlSl 301 0.1 1 0.57 0.99 0.026 0.015 17.20 7.58 0.012 0.04tracc 0.01 1 samples AISI 304 0.07 0.55 1.08 0.021 0.018 19.06 9.25 00150.03 trace 0.01s AISI 305 0.08 0.58 0.98 0.024 0.0l6 18.91 11.46 0.0250.05 (face 0.020 Cr-Ni-Cu-N 0.06 0.46 1.43 0.020 0.015 17.43 6.59 0.0002.05 [face 0.007 Cr-Ni-Cu 0.06 0.23 1.20 0.022 0.016 17.30 7.04 0.0241.94 mm. 0.01 1

'"us. Pill. No. 3211 6114 us. Pat. N0. 3.211 636 In Table 2, mechanicalproperties, martensite per- Table 3 to drawin and stretch- .Cemdge andproperties relating g step of drawing 1.91 2nd 3rd 41h mg of the Samplesof Table I are Shawl-L drawing drawing drawing drawing MartensitePercentage means the amount of mar Zi ra 411mm 315 mm 27.5 mm mm tensitethat is determined by a samplevibrating magne- 0 an tometer with samplesto which 40 percent elongation 4 mm 1. 2.03 2.33 2.61 b t f 70 mm 1.752.25 2.55 286 has een given at a strain ra e 0 m n 73 mm L83 232 2%Limiting Drawing Ration means a drawing ratio over 60 76 mm 1.90 2.412.76 3.10 which the delayed cracking occurs when sample sheets are drawnstepwise by means of the tools the dimension of which are shown in Table3. Table 2 shows that the The differences in delayed crackingsusceptibility besteels of this invention and AlSl 305 do not sufferdetween these steels are apparently demonstrated in the 65 layedcracking even if they undergo the most severe drawing test.

Although the steel of this invention and the steel of AlSl 305 aresimilar in that they are very resistant to attached drawing. Thespecimens shown in the drawing (photograph) are of the steel of thisinvention (48M0l AlSl 301, Cr-Ni-Cu-N steel and Cr'Ni-Cu steel from theleft to the right respectively. The sample sheet of 48M01 did not sufferdelayed cracking even after having undergone drawing of drawing ratio3.10. The sample sheet of A181 30] suffered remarkable delayed crackingafter having undergone drawing of drawing ration 2.03. The sample sheetof Cr-Ni-Cu-N steel suffered slight delayed cracking after havingundergone drawing of drawing ratio 2.41. The steel sheet of Cr-Ni-Custeel suffered delayed cracking after having undergone drawing ofdrawing ratio 2.32.

As has been explained in detail in the above, this invention provides anovel austenitic stainless steel which is provided with excellentdrawability and stretchability and remarkably resistant to delayedcracking, by restricting the total content of C and N in solid solutionstate to less than 0.04 percent and adding rather high amounts of Si andMn. The steel of this invention can be supplied at the price of the samelevel as that of A181 304.

What we claim is:

l. Austenitic stainless steel that is provided with excellentdrawability and stretchability and is highly resistant to delayedcracking essentially consisting of 1.0-2.5 percent Si, 1.5-5.0 percentMn, 1.0-4.0 percent Cu, 6.0-9.0 percent Ni, 15.0-19.0 percent Cr, -0.5percent of at least one of Al and Ti, not more than 0.06 percent C, notmore than 0.03 percent N and balance Fe and incidental impurities, inwhich the total 8 amount ol'(" 11ml l\ in the solid solution state isless than 0.04 percent.

2. The austenitic stainless steel as set forth in claim 1, whichessentially consists of 1.0-2.0 percent Si. 1.5-3.0 percent Mn, 1.0-3.0percent Cu, 6.5-8.5 percent Ni, 15.5-17.5 percent Cr, 0-0.4 percent ofat least one of Al and Ti, not more than 0.06 percent C, not more than0.03 percent N and balance Fe and incidental impuri ties, in which thetotal amount of C and N in the solid solution state is less than 0.03percent.

3. The austenitic stainless steel as set forth in claim 1, whichessentially consists of 1.2-1.8 percent Si, 1.8-2.8 percent Mn, 1.5-2.5percent Cu, 6.7-8 percent Ni, 16-17 percent Cr, 0-0.3 percent of atleast one of Al and Ti, not more than 0.06 percent C, not more than 0.03percent N in the solid solution state is less than 0.03 percent.

4. The austenitic stainless steel as set forth in claim 1, wherein atleast one of Al and Ti is contained in an amount of 0O.4 percent.

5. The austenitic stainless steel as set forth in claim 4, wherein atleast one of Al and Ti is contained in an amount 00.3 percent.

6. The austenitic stainless steel as set forth in claim 2, wherein atleast one of Al and Ti is contained in an amount 00.3 percent.

1. AUSTENITIC STAINLESS STEEL THAT IS PROVIDED WITH EXCELLENTDRAWABILITY AND STRETCHABILITY AND IS HIGHLY RESISTANT TO DELAYECRACKING ESSENTIALLY CONSISTING OF 1.0-2.5 PERCENT SI, 1.5-5.0 PERCENTMN, 1.0-4.0 PERCENT CU, 6.0-9.0 PERCENT NI, 15.0-19.0 PERCENT CR, 0-0.5PERCENT OF AT LAST ONE OF AL AND TI, NOT MORE THAN 0.06 PERCENT C, NOTMORE THAN 0.03 PERCENT N AND BALANCE FE INCIDENTAL IMPURITIES, IN WHICHTHE TOTAL AMOUNT OF C AND N IN THE SOLID SOLUTION STATE IS LESS THAN0.04 PERCENT.
 2. The austenitic stainless steel as set forth in claim 1,which essentially consists of 1.0-2.0 percent Si, 1.5-3.0 percent Mn,1.0-3.0 percent Cu, 6.5-8.5 percent Ni, 15.5-17.5 percent Cr, 0-0.4percent of at least one of Al and Ti, not more than 0.06 percent C, notmore than 0.03 percent N and balance Fe and incidental impurities, inwhich the total amount of C and N in the solid solution state is lessthan 0.03 percent.
 3. The austenitic stainless steel as set forth inclaim 1, which essentially consists of 1.2-1.8 percent Si, 1.8-2.8percent Mn, 1.5-2.5 percent Cu, 6.7-8 percent Ni, 16-17 percent Cr,0-0.3 percent of at least one of Al and Ti, not more than 0.06 percentC, not more than 0.03 percent N in the solid solution state is less than0.03 percent.
 4. The austenitic stainless steel as set forth in claim 1,wherein at least one of Al and Ti is contained in an amount of 0-0.4percent.
 5. The austenitic stainless steel as set forth in claim 4,wherein at least one of Al and Ti is contained in an amount 0-0.3percent.
 6. The austenitic stainless steel as set forth in claim 2,wherein at least one of Al and Ti is contained in an amount 0-0.3percent.